1. Field of the Invention
This invention relates to an apparatus and method for directing steam into a subterranean formation penetrated by a well. More particularly, the invention relates to an apparatus and method to receive steam injected down the well via a conduit and direct the steam against and into a selected section of a subterranean formation.
2. Description of the Prior Art
Steam injection is a well known method for stimulating the recovery of hydrocarbons from subterranean formations penentrated by a well. The method is especially applicable to recovery of highly viscous hydrocarbons having a high resistance to flow under normal subterranean conditions of temperature and pressure, but whose viscosity can be reduced and flow rate increased by the application of heat thereto. In the steam injection process as commonly practiced, steam is generated at the surface of the ground and injected down the well via an open-bottom-ended conduit. The steam exits the bottom of the conduit and enters the formation at the most permeable point along the well sidewall, wherever this most permeable point may be located. Thus, there is limited selectivity in the injection process. A packer cannot be used below the conduit to confine the steam to a limited area because during the steaming operation some formation particles slough into the hole and build up on top of the packer. Thus, the packer easily becomes stuck in the hole and cannot be readily removed following the steaming operation.
In the formation treating operations, it is often desired to inject steam into a particular stratum of the formation, which may or may not be the most permeable portion thereof. Additionally, it may be desired to inject steam first into one particular stratum of a formation for some time and then into another stratum of the formation. This is true where the formation is made up of alternate horizontal layers of an oil-containing strata and a shale strata. In using the open-bottom-ended conduit of the prior art, it was difficult to inject steam into anything other than the most permeable strata. Even when the position of the conduit is changed to be adjacent a second strata into which it was desired to inject steam, the steam still tended to go primarily into the most permeable strata which was previously treated.
Accordingly, a principal object of this invention is to provide an apparatus and method for injecting steam into selected strata of a subterranean formation.
Another object of the invention is to provide such an apparatus and method for successively steaming a plurality of oil-containing strata separated by shale strata.
Still another object of the invention is to provide such an apparatus and method which inject steam into such a formation with a minimum of erosion of the formation.
A further object of the invention is to provide such an apparatus which attaches to the bottom of the tubing and whose vertical position in the well can be changed between steam cycles by raising or lowering the tubing.
A still further object of the invention is to provide such an apparatus and method capable of injecting steam into a desired stratum of the formation without the aid of packers.
Other objects, advantages and features of the invention will be apparent from the following description.